 
package com.unsins.core.web.servlets;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.unsins.core.SystemConstants;

/**
 * 类说明
 *
 * @author odpsoft
 * @create  2008 2008-10-30 
 */
public class ImageServlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = -4268052368429271031L;

	private static final String CONTENT_TYPE = "image/png";

	private static final String FONT_TYPE = "DialogInput";

	private static final String IMAGE_TYPE = "PNG";


	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType(CONTENT_TYPE);
		response.setHeader("Pragma", "no-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);


		// 在内存中创建图象
		int width = 60, height = 20;
		BufferedImage image = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);

		// 获取图形上下文
		Graphics g = image.createGraphics();

		// 生成随机类
		Random random = new Random();

		// 设定背景色
		g.setColor(getRandColor(200, 250));
		g.fillRect(0, 0, width, height);

		// 设定字体
		g.setFont(new Font(FONT_TYPE, Font.ITALIC, 18));

		// 随机产生255条干扰线，使图象中的认证码不易被其它程序探测到
		g.setColor(getRandColor(160, 200));
		for (int i = 0; i < 255; i++) {
			int x = random.nextInt(width);
			int y = random.nextInt(height);
			int xl = random.nextInt(12);
			int yl = random.nextInt(12);
			g.drawLine(x, y, x + xl, y + yl);
		}

		// 取随机产生的认证码(4位数字)
		String sRand = "";
		for (int i = 0; i < 4; i++) {
			String rand = String.valueOf(random.nextInt(10));
			sRand += rand;
			// 将认证码显示到图象中
			g.setColor(new Color(20 + random.nextInt(110), 20 + random
					.nextInt(110), 20 + random.nextInt(110))); // 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
			g.drawString(rand, 13 * i + 6, 16);
		}

		// 将认证码存入SESSION
		HttpSession session = request.getSession();
		session.setAttribute(SystemConstants.SESSION_VERIFY_CODE, sRand);

		// 图象生效
		g.dispose();

		// 输出图象到页面
		ServletOutputStream outputstream = response.getOutputStream();
		ImageIO.write(image, IMAGE_TYPE, ImageIO
				.createImageOutputStream(outputstream));
		outputstream.flush();
		outputstream.close();
		outputstream = null;
		image = null;
	}

	private Color getRandColor(int fc, int bc) { // 给定范围获得随机颜色
		Random random = new Random();
		if (fc > 255) {
			fc = 255;
		}

		if (bc > 255) {
			bc = 255;
		}

		int r = fc + random.nextInt(bc - fc);
		int g = fc + random.nextInt(bc - fc);
		int b = fc + random.nextInt(bc - fc);

		return new Color(r, g, b);
	}
	
}

